Piping, header, and tubing arrangements for solar boilers

ABSTRACT

A header system for fluid circulation in a boiler includes a header configured to conduct fluid therethrough for circulating fluids in a boiler. A plurality of suction lines are connected in fluid communication with the header. Each suction line is configured and adapted to connect a respective pump in fluid communication with the header. A plurality of downcomers are connected in fluid communication with the header. Each downcomer is configured and adapted to connect the header in fluid communication with a steam drum. The header, suction lines, and downcomers are configured and adapted to draw substantially equal amounts of fluid from each of the downcomers even when flow is uneven among the suction lines. A plurality of cascaded headers can fluidly connect the circulation header to a steam generator. The plurality of cascaded headers is configured and adapted to provide a substantially equal flow to panels of the steam generator.

CROSS-REFERENCE TO RELATED APPLICATIONS

This application is a continuation in part of U.S. patent applicationSer. No. 12/547, 650, filed Aug. 26, 2009. This application is also acontinuation in part of U.S. patent application Ser. No. 12/620,109,filed Nov. 17, 2009. U.S. patent application Ser. Nos. 12/547,650 and12/620,109 each claim priority to U.S. Provisional Application No.61/151,984, filed Feb. 12, 2009, to U.S. Provisional Application No.61/152,011, filed Feb. 12, 2009, to U.S. Provisional Application No.61/152,035, filed Feb. 12, 2009, to U.S. Provisional Application No.61/152,049, filed Feb. 12, 2009, to U.S. Provisional Application No.61/152,077, filed Feb. 12, 2009, to U.S. Provisional Application No.61/152,114, filed Feb. 12, 2009, and to U.S. Provisional Application No.61/152,286, filed Feb. 13, 2009. Each of the above-referencedapplications is incorporated by reference herein in its entirety.

BACKGROUND OF THE INVENTION

1. Field of the Invention

The present invention relates to solar power production, and moreparticularly to boilers for solar power production.

2. Description of Related Art

Solar power generation has been considered a viable source to helpprovide for energy needs in a time of increasing consciousness of theenvironmental aspects of power production. Solar energy productionrelies mainly on the ability to collect and convert energy freelyavailable from the sun and can be produced with very little impact onthe environment. Solar power can be utilized without creatingradioactive waste as in nuclear power production, and without producingpollutant emissions including greenhouse gases as in fossil fuel powerproduction. Solar power production is independent of fluctuating fuelcosts and does not consume non-renewable resources.

Solar power generators generally employ fields of controlled mirrors,called heliostats, to gather and concentrate sunlight on a receiver toprovide a heat source for power production. A solar receiver typicallytakes the form of a panel of tubes conveying a working fluidtherethrough. Previous solar generators have used working fluids such asmolten salt because it has the ability to store energy, allowing powergeneration when there is no solar radiation. The heated working fluidsare typically conveyed to a heat exchanger where they release heat intoa second working fluid such as air, water, or steam. Power is generatedby driving heated air or steam through a turbine that drives anelectrical generator.

More recently, it has been determined that solar power production can beincreased and simplified by using water/steam as the only working fluidin a receiver that is a boiler. This can eliminate the need for aninefficient heat exchanger between two different working fluids. Thisdevelopment has lead to new challenges in handling the intense solarheat without damage to the system. In a solar boiler, heat transferrates can reach levels around 2-3 times the heat transfer rate of atypical fossil fuel fired boiler. This high heat transfer rateintensifies problems related to maintaining even heating and flowdistribution throughout known designs of boiler panels. The high heattransfer rate gives rise to high pressures and temperatures in theboiler tubing and related structures.

In typical forced circulation boilers, such as coal fired boilers,single or multiple circulation pumps are used to circulate water fromthe drum through the steam generator panels, and back into the drum as amixture of saturated water and steam. Traditional boilers often usemultiple circulation pumps operating in parallel for capacity andredundancy reasons. In a traditional configuration, a plurality of pumpsare connected in parallel along the length of a horizontal header, eachpump being connected to the header by way of a suction line. Thehorizontal header is in turn connected to the drum through a pluralityof vertical downcomers. Each pump draws water primarily from a specificportion of the drum through the nearest downcomers. In the event offailure of one or more of the pumps, the functioning pump or pumps drawuneven amounts of water from the drum through the different downcomers,creating an unbalance of flow in the drum. Unbalance along the length ofthe drum can lead to varying drum water level along the length of thedrum. Uneven water level in the drum can cause many problems includinghigh carry-under (when saturated fluid enters the downcomers) to a falselow water level alarm or low water level trip. Prolonged operation withlarge unbalances in drum water level can also lead to constant waterlevel alarms, water level trips, long-term fatigue and metallurgicalproblems from overheating, and affect the life and performance of thecirculation pump.

Another aspect of traditional boilers, such as coal fired boilers, isthat there are typically downcomers from the drum that feed fourwaterwall headers, namely two sidewall headers, a front wall header, anda rear wall header. Each of these headers, in turn, feeds a portion ofthe steam generator. This header arrangement, when applied to solarboiler applications, can lead to uneven flow from panel to panel, whichcan give rise to panel failure due to the intense heating describedabove. This, together with the with the circulation header arrangementdescribed above, can result in detrimental uneven flow throughout theboiler system, and causes a risk of emergency shutdown or even failureof key components.

Such conventional methods and systems have generally been consideredsatisfactory for their intended purpose. However, there is still a needin the art for boilers in general, and in particular solar boilers, thatallow for improved flow distribution between the drum and circulationpumps. There also remains a need in the art for such boilers withimproved flow distribution to the boiler panels. The present inventionprovides solutions for these problems.

SUMMARY OF THE INVENTION

The subject invention is directed to a new and useful header system forforced fluid circulation in a boiler. The system includes a headerconfigured to conduct fluid therethrough for circulating fluids in aboiler. A plurality of suction lines are connected in fluidcommunication with the header. Each suction line is configured andadapted to connect a respective pump in fluid communication with theheader. A plurality of downcomers are connected in fluid communicationwith the header. Each downcomer is configured and adapted to connect theheader in fluid communication with a steam drum. The header, suctionlines, and downcomers are configured and adapted to draw substantiallyequal amounts of fluid from each of the downcomers even when flow isuneven among the suction lines.

In accordance with certain embodiments, the header defines alongitudinal axis and has an inlet section and an opposed outlet sectionthat is spaced apart from the inlet section along the longitudinal axis.The suction lines are all connected to the outlet section of the header,and the downcomers are all connected to the inlet section of the header.

In certain exemplary embodiments, there are four downcomers, wherein aninner two of the downcomers are inboard with respect to two outboarddowncomers. Each inner downcomer is connected to the header at a firstcommon axial position on the header. Each outer downcomer is connectedto the header at a second common axial position on the header. The firstand second axial positions can be spaced apart axially along thelongitudinal axis of the header.

It is contemplated that the downcomers can be oriented perpendicular tothe header where connected thereto, and can all be oriented parallel toone another at inlet ends thereof. Similarly, one or more of the suctionlines can be oriented perpendicular to the header where connectedthereto, and parallel to one another at outlet ends thereof. Two suctionlines can be staggered axially or can be axially aligned with respect toone another where connected to the header. A third suction line can beconnected to the header in axial alignment therewith.

The invention also provides a solar boiler for solar power production.The solar boiler includes a steam generator and a superheater eachconnected in fluid communication with a steam drum. A plurality ofdowncomers are connected in fluid communication with the steam drum. Avertically oriented circulation header is fluidly connected to thedowncomers. A plurality of suction lines is in fluid communication withthe circulation header. The suction lines are each configured andadapted to place a circulation pump in fluid communication with thecirculation header. The circulation header, suction lines, anddowncomers are configured and adapted to draw substantially equalamounts of fluid from each of the downcomers even when flow is unevenamong the suction lines. It is contemplated that the circulation headercan have axially spaced apart inlet and outlet sections as describedabove, wherein the inlet section is above the outlet section.

The invention also provides a boiler for power production having aplurality of cascaded headers fluidly connecting a circulation header toa steam generator. The circulation header is configured to circulatewater from a steam drum into the steam generator. The plurality ofcascaded headers is configured and adapted to provide a substantiallyequal flow to panels of the steam generator.

In certain embodiments, the plurality of cascaded headers includes aflow path that passes through a series of progressively smaller headersfrom the circulation header to the panels of the steam generator. Therecan be at least three header sizes and/or levels between the circulationheader and individual tubes of the steam generator panels.

In accordance with certain aspects, a second plurality of cascadedheaders can be provided to fluidly connect the steam generator to thesteam drum to provide a saturated mixture of water and steam from thesteam generator to the steam drum. The second plurality of cascadedheaders can include a flow path that passes through a series ofprogressively larger headers from the panels of the steam generator tothe steam drum. There can be at least two header sizes and/or levelsbetween individual tubes of the steam generator panels and the steamdrum.

These and other features of the systems and methods of the subjectinvention will become more readily apparent to those skilled in the artfrom the following detailed description of the preferred embodimentstaken in conjunction with the drawings.

BRIEF DESCRIPTION OF THE DRAWINGS

So that those skilled in the art to which the subject inventionappertains will readily understand how to make and use the devices andmethods of the subject invention without undue experimentation,preferred embodiments thereof will be described in detail herein belowwith reference to certain figures, wherein:

FIG. 1 is a front elevation view of an exemplary embodiment of a solarboiler constructed in accordance with the present invention, showing thesolar boiler atop a solar receiver tower, with a cut-away portionshowing the steam drum and piping within the interior boiler space;

FIG. 2 is an elevation view of a portion of an exemplary circulationheader typical of the prior art, showing the horizontal headerarrangement;

FIG. 3 is an elevation view of a portion of the solar boiler of FIG. 1,showing the circulation header in a vertical header arrangement with theinlets and outlets of the header spaced out axially along the lengththereof;

FIG. 4 is an elevation view of another exemplary embodiment of acirculation header constructed in accordance with the present invention,showing two staggered suction lines connecting the header to tworespective pumps; and

FIG. 5 is schematic view of a portion of the solar boiler of FIG. 1,showing a cascading header arrangement for circulating fluids throughthe boiler panels.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

Reference will now be made to the drawings wherein like referencenumerals identify similar structural features or aspects of the subjectinvention. For purposes of explanation and illustration, and notlimitation, a partial view of an exemplary embodiment of a solar boilerin accordance with the invention is shown in FIG. 1 and is designatedgenerally by reference character 100. Other embodiments of solar boilersin accordance with the invention, or aspects thereof, are provided inFIGS. 3-5, as will be described. The systems of the invention can beused improve circulation reliability and flow distribution withinboilers, and particularly in solar boilers.

With reference now to FIG. 1, solar boiler 100 for solar powerproduction is shown at the top of a solar receiver tower 102, which canbe surrounded by a field of heliostats for focusing solar radiation onsolar boiler 100. Solar boiler 100 includes a plurality of solar boilerpanels 104 forming a perimeter surrounding a boiler interior space 106,which is visible through the cut-away portion in FIG. 1. A supportstructure 108 within boiler interior space 106 supports solar boilerpanels 104. Boiler panels 104 include a steam generator 110 with asuperheater 112 contiguous therewith on top of boiler 100, and with areheater 114 contiguous with steam generator 110 on the bottom of boiler100. Panels 104 for steam generator 110, superheater 112, and reheater114 are described in commonly owned, co-pending U.S. patent applicationSer. No. 12/552,724, filed Sep. 2, 2009, which is incorporated byreference herein in its entirety.

As can be seen in the cut-away portion of FIG. 1, a steam drum 116 ismounted to support structure 108 within boiler interior space 106.Boiler panels 104 define upper and lower extents of boiler interiorspace 106, and drum 116 is mounted below the upper extent of boilerinterior space 106. More particularly, drum 116 is mounted in interiorspace 106 within the elevation of superheater 112.

Since boiler panels 104 form a substantially contiguous heat transfersurface configured to block solar radiation incident thereon from boilerinterior space 106, drum 116 is protected by panels 104 from the intensethermal radiation incident on the solar receiver during operation. Solarboiler panels 104 form four boiler walls surrounding boiler interiorspace 106. Any other suitable number of walls can be used withoutdeparting from the spirit and scope of the invention. Four wall boilerconfigurations are described in greater detail in commonly owned,co-pending U.S. patent application Ser. Nos. 12/547,650 and 12/617,054,filed Aug. 26, 2009 and Nov. 12, 2009, respectively, each of which isincorporated by reference herein in its entirety. Downcomers 152 a, 152b, 152 c, and 152 d connected to steam drum 116 are also supported bysupport structure 108.

Referring now to FIG. 2, an example of a traditional steam drum 16 andcirculation header 50 are shown. Four downcomers 52 a, 52 b, 52 c, and52 d connect steam drum 16 to circulation header 50, which is in turnconnected to pumps 54 a, 54 b, and 54 c by way of suction lines 56 a, 56b, and 56 c, respectively. Under normal operation, pumps 54 a-54 ccirculate saturated water out from drum 16, through downcomers 52 a-52d, header 50, suction lines 56 a-56 c, through the steam generator, andback into drum 16 as a mixture of saturated steam and water. However, ifone or more of the pumps 54 a-54 c fails or otherwise loses capacity orreduces its flow rate, the fluid levels inside drum 16 will becomeuneven. For example, if pump 54 a stops working, suction line 56 a willeffectively be rendered inoperative. Since suction line 56 a is inclosest proximity to downcomers 52 a and 52 b, the flow in those twodowncomers 52 a and 52 b will be reduced much more than will the flow inthe more distant downcomers 52 c and 52 d. The result is that portionsof drum 16 proximate the openings into downcomers 52 a and 52 b willhave a higher fluid level than portions proximate downcomers 52 c and 52d, which may still provide suction at near-normal levels. The unevenfluid levels across drum 16 will create a flow unbalance in drum 16,which can cause high carry-under or a false low water level alarm or lowwater level trip. Prolonged operation with large unbalances in drumwater level can also lead to long-term fatigue and metallurgicalproblems arising from overheating drum 16.

Referring now to FIG. 3, the header system for fluid circulation inboiler 100 provides for even flow in the downcomers even when flow inone or more of the suction lines is reduced. The system includescirculation header 150 configured to conduct fluid therethrough forcirculating fluids in boiler 100. Three suction lines 156 a, 156 b, and156 c are connected in fluid communication with circulation header 150.Each suction line 156 a, 156 b, and 156 c is configured and adapted toconnect a respective pump 154 a, 154 b, and 154 c in fluid communicationwith circulation header 150. Four downcomers 152 a, 152 b, 152 c, and152 d are connected in fluid communication with circulation header 150.Each of the downcomers 152 a-152 d connects circulation header 150 influid communication with steam drum 116.

Header 150 defines a longitudinal axis A and has an inlet section 158and an opposed outlet section 160. Outlet section 160 is spaced apartaxially from inlet section 158 along the longitudinal axis A. Thesuction lines 156 a-156 c are all connected to outlet section 160, andthe downcomers 152 a-152 d are all connected to inlet section 158. Allof the fluid passing from inlet section 158 to outlet section 160 mustpass through a common section 162 between the outlets of downcomers 152a-152 d and the inlets of suction lines 156 a-156 c. Since all of thefluid must pass through common section 162, in the event flow throughone or more of suction lines 156 a-156 c is reduced relative to theothers, suction flow will be decreased for all of the downcomers 152a-152 d substantially evenly. Header 150, suction lines 156 a-156 c, anddowncomers 152 a-152 d are thus configured and adapted to drawsubstantially equal amounts of fluid from each of the downcomers 152a-152 d even when flow is uneven among the suction lines 156 a-156 cduring single or multiple pump operation. Flow rate can be completely orpartially reduced in a given pump due to a system failure, or withoutany failure, for example if it is desired to operate at a lower overallmass flow rate. The overall flow in such events would decrease, but thebalance of the flow would remain substantially uniform along drum 116and through downcomers 152 a-152 d. The problem of flow unbalance fromlosing one or more pumps is eliminated, which means the boiler cancontinue operating after loss of one or more pumps. This configurationalso reduces or eliminates ill effects from water level unbalanceincluding metal fatigue, overheating, boiler trips, and control issues.

The inner two downcomers 152 b and 152 c are inboard with respect to thetwo outboard downcomers 152 a and 152 d. Each of the inner downcomers152 b and 152 c is connected to header 150 at a first common axialposition 164 on the header, i.e., downcomers 152 b and 152 c connect toheader 150 at the same elevation along axis A. Each of the outerdowncomers 152 a and 152 d is connected to header 150 at a second commonaxial position 166 on header, i.e., downcomers 152 a and 152 d connectto header 150 at a common elevation along axis A, which is lower thanwhere inner headers 152 b and 152 c connect to header 150, as orientedin FIG. 3.

With continued reference to FIG. 3, downcomers 152 a-152 d are alloriented perpendicular to header 150 where connected thereto. All of thedowncomers 152 a-152 d are oriented parallel to one another at inletends thereof, i.e., where they connect to drum 116. Similarly, suctionlines 156 a and 156 c are oriented perpendicular to header 150 whereconnected thereto, and are parallel to one another at outlet endsthereof, i.e., where connected to the respective pumps 154 a and 154 c.The third suction line 156 b is connected to header 150 in axialalignment therewith. All of the suction lines 156 a-156 c and downcomers152 a-152 d are predominantly oriented parallel to circulation header150 and perpendicular to drum 116.

Referring now to FIG. 4, another exemplary embodiment of a header system200 constructed in accordance with the subject invention is shown.Header system 200 includes drum 216, downcomers, 252 a, 252 b, 252 c,and 252 d, circulation header 250 with longitudinal axis B, inletsection 258, outlet section 260, common section 262, pumps 254 a and 254b similar to those described above with respect to FIG. 3. Header system200 has two pumps 254 a and 254 b connected to circulation header 250 byway of two respective suction lines 256 a and 256 b. Rather thanconnecting to header 250 at a common elevation as do suction lines 156 aand 156 c in FIG. 3, suction lines 256 a and 256 b are staggered axiallywith respect to one another where connected to header 250. Since all thefluid must be pumped through common portion 262, even if one of the twopumps 254 a and 254 b loses power or s otherwise diminished or reducedin capacity or mass flow rate, flow through downcomers 252 a-252 d willremain substantially equal, and fluid levels in drum 216 will remainsubstantially even. Staggering inlets for suction lines 256 a and 256 bprovides advantages such as prevention of a false low level alarm or lowlevel trip, decreased carry-under, and increased pump performance.

Referring again to FIGS. 1 and 3, steam generator 110 and superheater112 are each connected in fluid communication with steam drum 116.Downcomers 152 a-152 d are connected to the bottom of steam drum 116where the fluid resides. Circulation header 150 is vertically orientedwithin boiler 100, as are downcomers 152 a-152 d, and suction lines 156a-156 c. In this vertical header orientation, the inlet section 158 ofheader 150 is above outlet section 160. While described herein in theexemplary context of having a vertically oriented circulation header,those skilled in the art will readily appreciate that a circulationheader can be oriented horizontally, or in any other suitableorientation and still achieve benefits, as long as the downcomers andsuction lines connect to the header in such a way as to providesubstantially even flow through the downcomers even when flow is unequalin the suction lines.

With reference now to FIG. 5, steam generator 110 of boiler 100 is shownschematically. Substantially equal flow rates to each solar receiverpanel 104 of steam generator 110 are provided by the system of cascadedheaders fluidly connecting circulation header 150 (not shown in FIG. 5,but see FIG. 3) to steam generator 110.

The circulation pumps, e.g., circulation pumps 154 a-154 c and 254 a-254b, feed into primary headers 168, as indicated in FIG. 5 by the arrowspointing into each primary header 168. The exemplary configuration shownin FIG. 5 has two lines feeding each primary header 168, such as if twocirculation pumps, e.g., 254 a and 254 b, each have two dischargenozzles/lines, with each pump feeding one line into each primary header168. In the event of one pump losing power, the remaining pump can stillfeed the entire steam generator 110 through both primary headers 168.Those skilled in the art will readily appreciate that the number ofpumps and/or lines feeding primary headers 168 can be varied withoutdeparting from the spirit and scope of the invention. For example, ifthree pumps are used, such as pumps 154 a-154 c, each pump can have twofeed lines, one to each primary header 168 so each primary header 168can be fed by all three pumps.

Each primary header 168 has four outlet lines, each connected to arespective secondary header 170, for a total of eight secondary headers170. Each secondary header 170 has eight outlet lines, with two outletlines feeding into each panel inlet header 172. In FIG. 5, thecomponents are all shown laid flat for clarity. Dotted line C indicateswhere the feed lines between secondary headers 170 and panel inletheaders 172 actually change direction in the constructed boiler 100,starting downward from the exits of headers 170, then bending upward atline C and continuing upward into panel inlet headers 172. Thisarrangement causes the flow through each panel to be in the upwarddirection. The benefits of having all steam generator panels in anup-flow configuration is described in greater detail in commonly owned,co-pending U.S. patent application Ser. No. 12/547,650.

Having two lines feeding each panel inlet header 172 helps provide evenflow through the tubes of the panels 104. Each panel 104 feeds into arespective panel outlet header 174. In FIG. 5, only one panel 104, onepanel inlet header 172, and one panel outlet header 174 are labeled withreference characters for sake of clarity. Each panel outlet header 174has two outlet lines that feed into an intermediate outlet header 176.Each intermediate outlet header 176 is fed by a pair of panels 104, andfeeds into steam drum 116 through a single feed line. Steam drum 116 isnot shown in FIG. 5, but the flow into drum 116 is indicated by arrowspointing out of the intermediate outlet headers 176.

The plurality of cascaded headers 168, 170, and 172 define a branchingflow path that passes through a series of progressively smaller headersfrom the supply (e.g., circulation header 150) to panels 104 of steamgenerator 110. There are three header sizes and three levels (168, 170,172) between the source (e.g., circulation header 150) and individualtubes of the panels 104 in steam generator 110. On the outlet side ofpanels 104, a second plurality of cascaded headers, i.e. headers 174 and176, fluidly connect steam generator 110 to steam drum 116 to provide asaturated mixture of water and steam from steam generator 110 to steamdrum 116. This second plurality of cascaded headers 174 and 176 definesa flow path that passes through a series of progressively larger headersfrom panels 104, through headers 174, into headers 176, and then intosteam drum 116. There are two header sizes and levels between individualtubes of the panels 104 of steam generator 110 and steam drum 116. Thisarrangement of cascaded inlet and outlet headers provides asubstantially balanced flow to the individual tubes of panels 104 insteam generator 110, since each header provides mixing and balancing.With multiple levels of mixing, balancing headers between relativelylarge components like circulation header 150 and relatively smallcomponents like the tubes of panels 104, there are multiple places forthe working fluid flow to mix and balance. Another benefit of havingmultiple stages of headers is that it facilitates modularization duringboiler construction, maintenance, repairs, and the like. A cascadedheader configuration, with increased number of headers, allows for theheaders to be smaller and therefore the headers can have thinner walls.Given that a solar boiler is typically cycled daily, going from a hotstate to a cold state, minimal wall thickness is advantageous forreducing creep, fatigue, and high stresses.

While described herein in the exemplary context of having three levelsof cascading inlet headers and two levels of cascaded outlet headers,those skilled in the art will readily appreciate that any suitablenumber of header levels can be used on the inlet and outlet sides ofboiler panels. Moreover, any suitable number or size of headers and feedlines can be used on any level of a cascaded inlet or outlet headersystem without departing from the spirit and scope of the invention. Thesystems and methods described herein provide particular advantages whenapplied to solar boilers, however those skilled in the art will readilyappreciate that the systems and methods described herein can be appliedto any other suitable type of boiler without departing from the spiritand scope of the invention.

The methods and systems of the present invention, as described above andshown in the drawings, provide for boilers, and particularly solarboilers, with superior properties including improved flow distributionin circulation components and receiver panels. While the apparatus andmethods of the subject invention have been shown and described withreference to preferred embodiments, those skilled in the art willreadily appreciate that changes and/or modifications may be made theretowithout departing from the spirit and scope of the subject invention.

1. A header system for fluid circulation in a boiler comprising: a) aheader configured to conduct fluid therethrough for circulating fluidsin a boiler; b) a plurality of suction lines connected in fluidcommunication with the header, each suction line being configured andadapted to connect a respective pump in fluid communication with theheader; and c) a plurality of downcomers connected in fluidcommunication with the header, wherein each downcomer is configured andadapted to connect the header in fluid communication with a steam drum,wherein the header, suction lines, and downcomers are configured andadapted to draw substantially equal amounts of fluid from each of thedowncomers even when flow is uneven among the suction lines.
 2. A headersystem as recited in claim 1, wherein the header defines a longitudinalaxis and has an inlet section and an opposed outlet section that isspaced apart from the inlet section along the longitudinal axis, andwherein the suction lines are all connected to the outlet section of theheader, and wherein the downcomers are all connected to the inletsection of the header.
 3. A header system as recited in claim 2, whereinthere are four downcomers, an inner two of the downcomers being inboardwith respect to two outboard downcomers.
 4. A header system as recitedin claim 3, wherein each inner downcomer is connected to the header at afirst common axial position on the header, and wherein each outerdowncomer is connected to the header at a second common axial positionon the header, and wherein the first and second axial positions arespaced apart axially along the longitudinal axis of the header.
 5. Aheader system as recited in claim 2, wherein the downcomers are orientedperpendicular to the header where connected thereto.
 6. A header systemas recited in claim 5, wherein the downcomers are all oriented parallelto one another at inlet ends thereof.
 7. A header system as recited inclaim 2, wherein one or more of the suction lines are orientedperpendicular to the header where connected thereto.
 8. A header systemas recited in claim 7, wherein the suction lines are all orientedparallel to one another at outlet ends thereof.
 9. A header system asrecited in claim 7, wherein two suction lines are staggered axially withrespect to one another where connected to the header.
 10. A headersystem as recited in claim 7, wherein two suction lines are axiallyaligned with respect to one another where connected to the header.
 11. Aheader system as recited in claim 7, wherein a third suction line isconnected to the header in axial alignment therewith.
 12. A headersystem as recited in claim 7, wherein two suction lines are axiallyaligned with respect to one another where connected to the header, andwherein a third suction line is connected to the header in axialalignment therewith.
 13. A solar boiler for solar power productioncomprising: a) a steam generator and a superheater each connected influid communication with a steam drum; b) a plurality of downcomersconnected in fluid communication with the steam drum; c) a verticallyoriented circulation header fluidly connected to the downcomers; and d)a plurality of suction lines in fluid communication with the circulationheader, the suction lines each being configured and adapted to place acirculation pump in fluid communication with the circulation header,wherein the circulation header, suction lines, and downcomers areconfigured and adapted to draw substantially equal amounts of fluid fromeach of the downcomers even when flow is uneven among the suction lines.14. A solar boiler as recited in claim 13, wherein the circulationheader defines a longitudinal axis and has an inlet section and anopposed outlet section that is spaced apart from the inlet section alongthe longitudinal axis, wherein the inlet section is above the outletsection, and wherein the suction lines are all connected to the outletsection of the header, and wherein the downcomers are all connected tothe inlet section of the header.
 15. A solar boiler as recited in claim13, further comprising a plurality of cascaded headers fluidlyconnecting the circulation header to the steam generator, wherein theplurality of cascaded headers is configured and adapted to provide asubstantially equal flow to panels of the steam generator.
 16. A boilerfor power production comprising: a) a steam generator and a superheatereach connected in fluid communication with a steam drum; b) acirculation header in fluid communication with the steam drum and thesteam generator for circulating water from the steam drum into the steamgenerator; and c) a plurality of cascaded headers fluidly connecting thecirculation header to the steam generator, wherein the plurality ofcascaded headers is configured and adapted to provide a substantiallyequal flow to panels of the steam generator.
 17. A boiler as recited inclaim 16, wherein the plurality of cascaded headers includes a flow paththat passes through a series of progressively smaller headers from thecirculation header to the panels of the steam generator.
 18. A boiler asrecited in claim 17, wherein there are at least three header sizesbetween the circulation header and individual tubes of the steamgenerator panels.
 19. A boiler as recited in claim 16, wherein a secondplurality of cascaded headers fluidly connects the steam generator tothe steam drum to provide a saturated mixture of water and steam fromthe steam generator to the steam drum.
 20. A boiler as recited in claim19, wherein the second plurality of cascaded headers includes a flowpath that passes through a series of progressively larger headers fromthe panels of the steam generator to the steam drum, wherein there areat least two header sizes between individual tubes of the steamgenerator panels and the steam drum.